Biomedical subjects
Publications and source records attributed to E Katayama.
The interaction of troponin-I (TN-I) and troponin-T (TN-T) was examined using immobilized TN-2 as an affinity adsorbent. TN-T dissolved in 0.4 M NaCl bound strongly to immobilized TN-I and required the application of 5 M urea for its elution. A chymotryptic fragment of TN-T (Ohtsuki, 1978), perhaps the C-terminal fragment, retained the ability of the original TN-T to bind to immobilized TN-I.
The fine structure of the purified actin filament was investigated by negative staining. The actin filament polymerized in Tris-HCl buffer and KCl showed a collapsed image different from that of a double stranded helix. Addition of ATP, ADP, or inorganic orthophosphate, however, converted it into a straight filament with typical double strands.
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Images of shadowed F-actin filaments on mica surfaces obtained using a quick-freeze, freeze-fracture, deep-etch technique were subjected to conventional 3-D helical reconstruction methods. Although the shadowing must vary systematically from subunit to subunit, the computed transforms of isolated filaments were characteristic of the helical actin transform. Helical reconstruction was therefore judged to be valid. The theoretical basis for such reconstruction is outlined. The reconstructions showed an average thin (about 3 nm) layer of shadow on the filament surface and both the outer and the inner surfaces of the shadow layer could be visualized. By comparison with the F-actin structure postulated by Holmes et al. (1990) on the basis of the known structure of the actin monomer, it is shown that, at the resolution considered, the inner surface of the shadow provides a reasonably faithful outline of the molecular surface. This, in turn, confirms that the original 3-D structure of the protein molecules has been well preserved throughout the whole preparation procedure up to the final replica. The "shadowed" filaments can thus be correlated axially and azimuthally with known actin structures and, in principle, features such as myosin head location on decorated filaments can be determined. The result emphasizes the amount of detail present in good quality images of shadowed particles and, in this case, shows that detailed evaluation of molecules labeling actin can be made.
The autoradiographic localization of alpha 1- and alpha 2-adrenoceptors was identified in 22-week-old Wistar-Kyoto rat kidney, using alpha 1-selective ([3H]bunazosin) and alpha 2-selective ([3H]yohimbine) antagonists. [3H]Bunazosin binding was distributed predominantly over the cortex, less over the outer medulla and was absent from the inner medulla. [3H]Yohimbine binding was distributed predominantly over the medulla, less over the renal cortex and was absent from the inner medulla. In addition, the distribution of renal alpha-adrenoceptors was investigated in 3-, 7- and 22-week-old spontaneously hypertensive rats (SHRs) using a computerized image analysis system. Renal alpha-adrenoceptors were both found to be increased in SHRs at all ages tested compared with their respective controls and were increased in both the cortex and the outer medulla. The increase in renal alpha-adrenoceptors was already present in 3-week-old SHRs whose systolic blood pressures did not differ significantly from those of the controls. The results strongly suggest that these abnormalities of renal alpha-adrenoceptors may play a critical role in the development of hypertension in SHRs.